This essay presents the Aestheticism of the 19th century as the foundational movement
of modernist-formalist aesthetics of the 20th century. The main principle of this movement is
what I denominate “productive opacity”. Aestheticism has not been recognized as a philosophical
aesthetic theory. However, its definition of artwork as an exclusive kind of form—a deep, opaque
form—is among the most precise ever given in the discipline. This essay offers an interpretation
of aestheticism as a formalist theory, referred to here as “deep formalism”, focusing on the thinking
of leading aestheticists, Walter Pater, Oscar Wilde, and James Whistler. These three thinkers
defined artwork as a form saturated with an inextricable content, viz. opaque form.